Those frequently used as the hydrorefining catalyst in the petroleum refining include a catalyst in which a hydrogenation-active metal component, which has the hydrogenation ability, is carried on an alumina carrier. In the hydrorefining, the hydrocarbon oil and the hydrorefining catalyst are allowed to make contact with each other in the presence of hydrogen, in which it is possible to remove heteroelements contained in the hydrocarbon oil, i.e., sulfur, nitrogen, and metal components (for example, vanadium, nickel, and iron). A variety of investigations have been hitherto made in relation to the catalyst as described above, for example, about the active metal, the properties of the carrier, the pore structure, and the method for carrying the active metal in order to improve the ability to remove the heteroelements.
A hydrorefining catalyst having a high activity is obtained by using, as a carrier for the hydrorefining catalyst, an alumina carrier which can be manufactured by kneading and forming a fine powder of pseudo-boehmite as an alumina hydrate, followed by being calcinated. A phosphorus component is sometimes contained in the hydrorefining catalyst. The phosphorus component is carried such that the component is contained in a carrying solution in some cases, or the phosphorus component is added when the carrier is manufactured in other cases. For example, in Japanese Patent Application Laid-open No. 61-254254 (corresponding to U.S. Pat. No. 4,624,938), a catalyst carrier is manufactured by adding a phosphorus-containing compound to a precipitate of alumina hydroxide, followed by being calcinated.